Comparison of Geometric characterizes Chehel-chay Forest Watershed Roads With Rural Road Standards with an Emphasis of Run off Product

Roads induce some of the most pervasive anthropogenic alterations in watershed and source o run off. In mountain area road network despite of lower surface to total surface has impact the watershed hydrology. The aim of the current research is comparison of Chehel-chay Watershed roads whit rural road standards and runoff calculate of these roads.
The existing road network map was created on 1:25,000 scale (NCC), using satellite image and mapping by GPS using Arc GIS10.1.The technical characteristics roads i.e. traveled way, width, cut and shoulder width, cut and slop, road lengths slop and ditch were recorded and compared whit rural road standards using One-sample T- Test in SPSS. Then, the profile of roads in current and standard situation was created using Civil 3D and the run off these road calculated using length and width oo roads, run off coefficient and precipitation per m3 for existing roads per km in year.
Length and density of the road network in the study area are 337.07 km and 13.12mha-1, respectively. The results show that length slope and cut slop in high class >6 meters of asphalt roads, in gravel roads cut and shoulder width, lengths slop and cut slop in high class >6 meters and in dirt roads lengths slop and cut slop in high class >6 meters are significant different with standards. The results indicate that 43.06%, 39.02%, 33.42% pre m3/km in year the run off of existing asphalt, gravel and dirt roads, respectively more than standard situation.
The different between roads in existing and standard situation whether explain just by statistics can not realize the expert with failing to comply of standards. The difference between existing and standard situation showed that at the time of manufacture can reduce side effects caused by the construction of roads. In this research the runoff in existing situation about 39% more than standards for total roads. Estimation the run off of roads is effective criteria in order to distinguish of destructive effects of roads without consider to standards, is the main finding of current research. The different between roads in existing and standard situation whether explain just by statistics can not realize the expert with failing to comply of standards. The difference between existing and standard situation showed that at the time of manufacture can reduce side effects caused by the construction of roads. In this research the runoff in existing situation about 39% more than standards for total roads. Estimation the run off of roads is effective criteria in order to distinguish of destructive effects of roads without consider to standards, is the main finding of current research.